Field of the Invention
The present disclosure relates to digital watermarking, and more specifically, to anti-collusion watermarking.
Background
The purpose of forensics marking is to facilitate the identification of leaking audio-visual sources. As such, the forensic marking may complement other investigation tools. The aim is to discover the compromised device or the set of compromised devices, or the infringing viewer.
One known attack is called collusion. Two or more, colluding principals mix in some way their individually watermarked pieces of content with the hope that the attack either erases the embedded information or points to another principal.
One commonly proposed solution is to use payloads supporting anti-collusion. They are often referred to as Tardos codes and many researchers followed the principles of Tardos codes. Tardos codes allow detection with high probability of the collusion of two or more colluders.
The main problem with Tardos codes is that they require a payload length of several hundreds or thousands of bits. Long payloads may be only practical with usual digital watermarking strategies using the full length of the piece of content to embed many successive occurrences of the payload. Unfortunately, it may not be true for sequence key-like watermarking strategies, which typically do not support long payloads.